Added invoices and invoicelines.
Latest work on the invoice-implementation.
Merge remote-tracking branch 'origin/master' into kj/invoices_impl

Conflicts:
	config/locales_gettext/da/LC_MESSAGES/default.mo
	config/locales_gettext/da/LC_MESSAGES/default.po
	config/locales_gettext/static_translation_file.json
	db/schema.rb
More work on invoices: Able to save invoice-lines (not finished).
Added PDF generation. Extended customer fields to contain several invoice fields. Added specs for invoices and customers.
Updated cache.
Merge remote-tracking branch 'origin/master' into kj/invoices_impl
Merge remote-tracking branch 'origin/master' into kj/invoices_impl
Added creditors to invoices for credit invoices and eventual tax calculation.
A lot of work on managing uploaded files. Also test for this.
Implemented Rails Imager for dynamic showing of images.
Added totals, fixed spelling errors and some more.
Added payment info, vat no and a lot of other essential information. Design for invoices. A lot of finishing touches.
Merge pull request #54 from kaspernj/kj/invoices_impl

Added invoices and invoicelines.