BPathFinder: include StringList.h for convenience.

* You cannot do anything with a path finder object without a string
list, so why go through all the hassle?

BPathFinder: Add BPackageResolvableExpression initialization

Add a constructor and a SetTo() method with a
BPackageResolvableExpression parameter instead of a path. The path of
the package satisfying the expression is used.

The new functionality lives in libpackage as it uses the package kit.

BPathFinder: Coding style improvements

Add get_*architecture() API, extend find_path*() API

* Add get_architecture(), get_primary_architecture(),
get_secondary_architectures(), guess_architecture_for_path() to get
the caller's architecture, the primary architecture, all secondary
architectures, or the architecture associated with a specified path
respectively.
* Rename the find_path*() functions to find_path*_etc() and add an
optional architecture parameter. Add simplified find_path*()
functions.
* BPathFinder: Add FindPath[s]() versions with an architecture
parameter.

Add class BPathFinder

It's a more convenient C++ wrapper for the new find_path*() C functions.

BPathFinder: include StringList.h for convenience.

* You cannot do anything with a path finder object without a string
list, so why go through all the hassle?

BPathFinder: Add BPackageResolvableExpression initialization

Add a constructor and a SetTo() method with a
BPackageResolvableExpression parameter instead of a path. The path of
the package satisfying the expression is used.

The new functionality lives in libpackage as it uses the package kit.

BPathFinder: Coding style improvements

Add get_*architecture() API, extend find_path*() API

* Add get_architecture(), get_primary_architecture(),
get_secondary_architectures(), guess_architecture_for_path() to get
the caller's architecture, the primary architecture, all secondary
architectures, or the architecture associated with a specified path
respectively.
* Rename the find_path*() functions to find_path*_etc() and add an
optional architecture parameter. Add simplified find_path*()
functions.
* BPathFinder: Add FindPath[s]() versions with an architecture
parameter.

Add class BPathFinder

It's a more convenient C++ wrapper for the new find_path*() C functions.