Add extrafield tables
- New: [ task #926 ] Add extrafield feature on order lines
- New: [ task #927 ] Add extrafield feature on Proposal lines
- New: [ task #928 ] Add extrafield feature on invoice lines
Merge branch 'develop' into develop_926_927_928

Conflicts:
	htdocs/core/class/extrafields.class.php

Change-Id: Ia54e1be6954bc28f81122e88e398bda8059ab536
Merge pull request #1040 from FHenry/develop_926_927_928

task 926 927 928