tools: State jinja2 version

Provides a graceful error when jinja2 is the wrong version

Remove references to unused tempita library

tools: Fix whitespace differences in header gen

libsel4: change tempita to jinja2

tools: fix licenses

libsel4: fix licenses

- some were incorrectly marked GPL (libsel4 is BSD)
- update NICTA --> DATA61 etc
- fix tags D61 --> DATA61
- update year to 2017

tools: Correct case where label numbers will be 0

If `seL4_arch_invocations` is an empty list, this will cause `nSeL4ArchInvocationLabels`
to be declared as 0, rather than `nInvocationLabels` as intented. This change correctly
respects the behaviour of the 'first' variable, and does an explicit assignment to
`nSeL4ArchInvocationLabels` should it be the first (and only) member of the enum.

Closes #53

update #ifdef to #if in auto generated files

tools: Remove arithmetic in invocation generation

If invocations are hidden behind config guards the count of how
many invocations there are will be wrong. The C compiler will
correctly assign the value with enum auto numbering, so there's
no need to override that here

tools: emit error if first invocation conditional

Placing a config condition on the first define
in sel4arch.xml will fail as currently the first define
must start at the last define + 1 of the previous
invocation enum.

If this is ever required, autoconf.h will need to be passed
to the script so it can check config variables itself.

tools: add conditional invocation label defines

tools: add conditional invocation label defines

tools: invocation_header_gen: python3 compat

tools: invocation_header_gen: remove trailing whitespace

libsel4: Explicitly generate number of invocation labels to handle case where there are no invocations

libsel4: Generate libsel4 definitions from the current ARCH as well as the SEL4_ARCH

Use usr/bin/env for all python bangpaths to enable virtualenv use.

Very useful with python3 as the default platform.

Release snapshot