Allow user to set static page before saving

fixes #1350
- jQuery event.preventDefault() stops the user from selecting the checkbox
Add support for SVG images
Move plugin init code into plugin.js and have it called from server.js
Update CONTRIBUTING.md
Merge pull request #1462 from hswolff/plugin-init-cleanup

Move plugin init code into plugin.js and have it called from server.js
Merge pull request #1458 from mjbshaw/svg

Add support for SVG images
Pass proxy Ghost interface to Apps

Closes #1478

- Create new proxy.js that exposes createProxy method
- Pass proxy to App activate/install in lieu of Ghost instance
Adding recommended fields to package.json
Fix wrong error message

closes #1466
- added status code for error object
- added test for frontend errors
Remove inline script from default.hbs

closes #1268
Lowercase email address.

fixes #1498
Add schema.js

closes #1398
closes #1399
closes #1400
- added schema.js with database version '000'
- refactored migration to use schema.js
- if new table is added to schema.js and databaseVersion is increased, table will be added
- if new table is deleted to schema.js and databaseVersion is increased, table will be deleted
- alter table from issue #1400 is delayed until knex supports column modification
- changed import pre checks to work again (will be refactored separately)
- added basic PostgreSQL support (Attention: not supported/tested)
- changed error handling in server.js
Merge pull request #1489 from sebgie/issue#1466

Fix wrong error message
Merge pull request #1505 from halfdan/1498-lower-email

Lowercase email address.
Merge pull request #1353 from thgaskell/1350-static-page-checkbox

Allow user to set static page before saving
Correct the Markdown for emphasis
Merge pull request #1485 from Archanium/MinorIssues

Danish language file and a correction to Markdown modal
Merge pull request #1449 from sebgie/issue#1398

Add schema.js
Reduce size of ghost.js by moving related Routing code to their own files
Move server middleware configuration to related file