refactor invoices page1 and page2
Merge pull request #131 from MargaretLangley/master

refactor invoices front page
disable form for editing until a range of properties has been selected
Merge branch 'master' of github.com:BCS-io/letting
Invoicing delivering / retained 'none' messages
Client 'no properties' message using partial and tested for both states.
Client using partial for "no properties" - refactored tests
Invoice view sheet, centralized, products alignment/col width adjusted. Sissor line view font adjusted.