Introduce kmm_csvimport_core

Purpose of this patch is to get rid of kmm_csvimport_static.
Advantages:

1. no bulky kmm_csvimport_static,
2. test cases can use kmm_csvimport_core directly,
3. CSV importer is even more separate from CSV wizard than before,
4. webpricequote update now can link only to CSV importer without

wizard,

5. webpricequote and CSV Wizard use the same binary (i.e. shared

library),

6. kmymoney binary + shared library + plugin library is about 15 MB

smaller, than before.

7. new csvenums.h which helps setting profiles for webpricequote.
8. CSV Importer needs no kmymoney_common module
9. MyMoneyQifReader::checkCategory and CsvUtil::checkCategory have been

deduplicated and put into mymoneyfile.cpp; KMyMoneyApp::createAccount
follows and fits "almost perfectly" in mymoneyfile.cpp.

10. csvutil.cpp and convdate.cpp has been rewritten and cleaned up -

lots of redundant code.

Differential Revision: https://phabricator.kde.org/D6300

Signed-off-by: Łukasz Wojniłowicz <lukasz.wojnilowicz@gmail.com>