Add a note on target_field #116
Add some addtional notes on the post processor doc #124
Add notes on aggregation types #124
Add some notes on minimum needs post processor #124
Add some notes on minimum needs post processor #124
merge conflicts
Add a note on target_field #116
Add some addtional notes on the post processor doc #124
Add notes on aggregation types #124
Add some notes on minimum needs post processor #124
Add some notes on minimum needs post processor #124
merge conflicts
Merge branch 'develop' of https://github.com/assefay/inasafe-doc into develop

Conflicts:
	docs/source/developer-docs/writing_impact_functions.rst
Minor correction
Minor/typo corrections
Merge pull request #150 from assefay/develop

Minor updates for dev docs (writing impac functions and post processors)