More work on module texts, and especially on the collector 

The members SetIgnoreMTextsOnCopper, SetIgnoreMTextsOnCmp,
SetIgnoreModulesOnCu, SetIgnoreModulesOnCmp in the collector guide are
renamed to the clearer SetIgnoreMTextsOnBack, SetIgnoreMTextsOnFront,
SetIgnoreModulesOnBack, SetIgnoreModulesOnFront

Modified the collector and drawing behaviour for text in modules as
discussed in the mailing list.

* Now module text on layers different than Silk should work! *

Still need UI support for setting the layer in the module editor.