DriverSettingsMessageAdapter: added "wildcard" support.

* You can now add arbitrarily named fields to the message as well,
without having them all specified in the template.
* Also added a missing converter method that is called when there
are no values to add, and implemented all methods in the base
class, so that you only have to implement the methods you actually
need.

DriverSettingsMessageAdapter: fixed converter signature.

* The ConvertFromDriverSettings() method missed the current value
index.
* Completed unit tests, and enabled them all.

DriverSettingsMessageAdapter: fixed various issues.

* _AddParameter() would ignore all BMessage::Add*() errors.
* _ConvertFromDriverParameter() would ignore most intermediate error,
but would fail badly over some incorrect settings file.
* Also, it checked for the parent value for each parameter, which
doesn't make any sense, but would add as often as there are
parameters -- which also may be none, in which case the value
got ignored.

DriverSettingsMessageAdapter: hide empty message.

* Empty messages no longer end up as empty section - instead, they are
just empty.

DriverSettingsMessageAdapter: optional field converter.

* You can now optionally specify a converter that does the actual
message to settings conversion, and vice versa.
* This allows for more sophisticated and custom conversions.

include strings.h where appriopriate...

instead or additionally to string.h, in preparation for functions move.
* moves str[n]casecmp() functions and others to strings.h.
* strings.h doesn't include string.h anymore.
* this solves #10949

More small C++11 tweaks.

libshared: Factored out driver settings class from net_server.

* The new class is called DriverSettingsMessageAdapter which can translate
between a driver_settings file, and a BMessage.
* The net_server Settings class is now just using this class.

DriverSettingsMessageAdapter: added "wildcard" support.

* You can now add arbitrarily named fields to the message as well,
without having them all specified in the template.
* Also added a missing converter method that is called when there
are no values to add, and implemented all methods in the base
class, so that you only have to implement the methods you actually
need.

DriverSettingsMessageAdapter: fixed converter signature.

* The ConvertFromDriverSettings() method missed the current value
index.
* Completed unit tests, and enabled them all.

DriverSettingsMessageAdapter: fixed various issues.

* _AddParameter() would ignore all BMessage::Add*() errors.
* _ConvertFromDriverParameter() would ignore most intermediate error,
but would fail badly over some incorrect settings file.
* Also, it checked for the parent value for each parameter, which
doesn't make any sense, but would add as often as there are
parameters -- which also may be none, in which case the value
got ignored.

DriverSettingsMessageAdapter: hide empty message.

* Empty messages no longer end up as empty section - instead, they are
just empty.

DriverSettingsMessageAdapter: optional field converter.

* You can now optionally specify a converter that does the actual
message to settings conversion, and vice versa.
* This allows for more sophisticated and custom conversions.

include strings.h where appriopriate...

instead or additionally to string.h, in preparation for functions move.
* moves str[n]casecmp() functions and others to strings.h.
* strings.h doesn't include string.h anymore.
* this solves #10949

More small C++11 tweaks.

libshared: Factored out driver settings class from net_server.

* The new class is called DriverSettingsMessageAdapter which can translate
between a driver_settings file, and a BMessage.
* The net_server Settings class is now just using this class.