Rename macros

Rename the macros that prevent a header to be included more than once
Prevent Find-Dialog to automatically look for dates

The Student-Lend, Teacher-Lend and Swap sections of the Find-Dialog used to
automatically include the date 01/01/2000 into their search query. Introducing
three new variables that hold whether the specified date was changed, this is
now fixed.
Merge remote-tracking branch 'github/master'