parameter 'source' must not be ignored in DevSearch.ThisText. Refs: #88.
StdApi uses the name 'useLang' for the same kind of parameters.
Therefore it has been renamed from 'source' to 'useLang' and the meaning is inverted.
Searching in Mod (source code) is language independent now.
Searching in Docu is still language dependent.

Signed-off-by: Josef Templ <josef.templ@gmail.com>