Allow setting the following items from outside:
* capture regular expression,
* file name, line number and message capture position and
* whether to parse stdout, stderr or both

The parser functions can be unit-tested by running (Debug build of Qt
Creator needed):

qtcreator -test ProjectExplorer,testCustomOutputParsers

The data is passed to the custom parser in
CustomToolChain::outputParser().

The parser information is stored in toolchains.xml together with the
custom toolchain. A configuration widget is provided to set up and test
the regular expression against a sample error message.

Change-Id: I6191df3c44432943e0aeb16c48d8e79d35845d2e
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>