Improving the content assist in text fields (refs #2969):

Improving the content assist in text fields (refs #2969):
* ESC no longer destroys all changes if pressed when the popup box is open
* The equation doesn't need to be delimited by whitespace to make the auto completion work.
* The cursor is put in between the parenthesis of functions
* Variables are on top of the list
Small fix to completion processor in the charts: '_' character is now allowed too

git-svn-id: https://www.simantics.org/svn/simantics/sysdyn/trunk@25710 ac1ea38d-2e2b-0410-8846-a27921b304fc