Support for additional macros from import package

[janniklasrose]

Fixes #239

I have

• changed the regular expression that handles the import commands to now detect all three macros provided by the import package.
• tried to make the documentation a bit clearer.
• added test files to the testsuite

[ftilmann]

Thank you for this improvement and apologies for the very long lag time until I was able to test this. Thank you in particular for providing a test case.