Add initial unit testing for the guile-pcb Scheme API.

* Makefile.am:
* configure.ac: Modified to support tests/ directory.

* tests/Makefile.am:
* tests/test-guile-pcb.c: Added override for path to bootstrap file.

* tests/pcb.scm: Added special bootstrap file for tests.

* tests/run-test.sh: Added runner for tests.

* tests/action.test:
* tests/api.test:
* tests/hid.test:
* tests/object.test: Added test files.

* tests/Makefile.am:
* tests/guile-pcb.api: Added description of Scheme API exported.

* .bzrignore: Inserted new patterns for tests.