handling of file extensions

[ColdIV]

The handling of file extensions is currently not clear.

It should be one of the following:

• all scripts (programs and libraries) should have the .lua extension
• only scripts within the subfolders should have the .lua extension
• all scripts (programs and libraries) should have the .lua extension, excluding programs in root

I think its best to just add the extension to all files. The only downside would be that, if you program something within MC, you have to remind yourself to add the extension to the program.
That shouldn't be too hard.

If all files should get the file extension, then #20 should not be merged.

[ColdIV]

it will be option 1) all scripts (programs and libraries) should have the .lua extension

[ColdIV]

resolved by #32