Fixes #2641 - Add type_changed check to JS to allow form to refresh when provisioning a discovered host
Fixes #2642 - Display build button if host type has changed
Fixes #2643 - Check for operatingsystem before orchestrating TFTP
Fixes #2644 - Refactor Host find_by_name to use several ways to find a
host, and refactor my_hosts scope to Host::Base, allowing us to remove
unnecessary permissions check from find_by_name
fixes #2343 - override default settings with custom values

- added check for nil before attribute 'default' is loaded from yaml
- removed logic that tried to set 'value' attr to nil when it was equal to 'default';
  it didn't behave predictably as 'default' can be assigned after 'value'
fixes #2660 - settings, improve tests and fixes

- added string settings type
- fixed tests previously commented out due to CI failures
- more tests for core settings functionality
- parsing of string values enhanced and extracted to a separate method
- setting value to nil when it equals default is back
- create! is now prefered method for creating settings as it raises exceptions on invalid states
- setting takes string as default type when parsing values from user input
fixes #2334 - location matcher doesn't match on smart parameters
fixes #2564, #2658 - apipie requirement bumped
Fixes #2657 - Use twitter-bootstrap-rails version 2.2.6
Fixes #2619 - don't display full output from proxy

Proxy output is logged alongside with backtrace of exception. We display
only exception message in UI.