Feature alib2dummy as sample library extension

Separate the alib2dummy project from sources and make it a base for datastructure/algorithm extension library.

added T-feature label

Are the DataType algorithms in alib2dummy useful or can we discard them? I'd like this to be done for the next year students.

They are present as examples so that newcomers can start development easily. Do whatever you like with the whole alib2dummy.

OK, I modified it only a bit.

Blocked by:

• #191 (do not install alib2dummy)
• website documentation for alib2dummy as a starting point
• aql2 should link alib2dummy but not if installing (releasing)... This is gonna take some thinking how to achieve this (maybe only in debug mode?)

mentioned in commit b3e26793

mentioned in commit 3a2990f9

mentioned in commit 13b50b06