rapidftr/tracker#180 syncing enquiries.

@ctumwebaze @mwangiann
When synchronizing enquiries from the mobile to the web, it was failing due to that fact that the mobile
device was sending along particular fields that are couchdb system fields i.e '_rev' that were causing conflicts.

This fix extends the functionality of the enquiries to allow.
1. creation of a unique identifier for an enquiry before saving it. This is important because the mobile device requires this
field to be present to avoid creation of duplicate records when synchronizing.
2. dealing with history logs of an enquiry during synch.
Merge pull request #721 from ctumwebaze/master

rapidftr/tracker#180 syncing enquiries.
rapidftr/tracker#187 @andreweskeclarke @mwangiann Adding searchable attribute to fields
rapidftr/tracker#187 @andreweskeclarke @mwangiann Allowing admin to mark fields as searchable, and use only searchable fields for matching enquiries to children
rapidftr/tracker#187 @andreweskeclarke @mwangiann Renaming searchable attribute on fields to matchable
rapidftr/tracker#187 @andreweskeclarke @mwangiann Including faker for development sample data creation
rapidftr/tracker#187 @andreweskeclarke @mwangiann Adding translation for Matchable
rapidftr/tracker#187 @andreweskeclarke @mwangiann Fixing rubocop violations
rapidftr/tracker#187 @andreweskeclarke @mwangiann Fixing broken browser test
Merge pull request #722 from andreweskeclarke/master

rapidftr/tracker#187 - Mark Enquiry fields as Matchable
rapidftr/tracker#187 @andreweskeclarke @mwangiann Removing requirement that criteria exist on an enquiry
rapidftr/tracker#187 @andreweskeclarke @mwangiann Fixing rubocop violation
Merge pull request #723 from andreweskeclarke/master

rapidftr/tracker#187 @andreweskeclarke @mwangiann Removing requirement t...
Merge branch 'master' of github.com:rapidftr/RapidFTR

Conflicts:
	app/models/enquiry.rb