Added CmakeLists.txt for building the plugin
Fixed SubsystemBuilder function in Skeleton plugin

The system class convention needs the get<TYPE>SubsystemBuilder
function to have type in caps lock, otherwise the
pfw will loop infinitely when attempting to load plugin.
Added comments for new plugin developers

As a new pfw plugin developer, i encountered an undocumented
(in the plugin) naming issue related to how the pfw
loads subsystem builders.

This patchs just added a comment to inform other
developers not to make the same mistake
Merge pull request #7 from kir0gawa/skeleton-plugin-fixes

Skeleton plugin fixes