Fixes #374. initial version

Implement update-check and update commands in commands API to check and update rockstor
Merge branch 'issue#374_updates_from_webui' of https://github.com/schakrava/rockstor-core into schakrava-issue#374_updates_from_webui
add default service presets for rockstor appliance
Merge branch 'master' into schakrava-issue#374_updates_from_webui
Merge branch 'issue#374_updates_from_webui' of github.com:schakrava/rockstor-core into schakrava-issue#374_updates_from_webui
Updates from webui

Add update check timer
Add current version and update icon in navbar
Add view and template for update.
Update functionality for version view
simplify the update-check process to provide a list -- (cur_version,
latest_version, [changelog,])
Merge branch 'issue#374_updates_from_webui' of github.com:schakrava/rockstor-core into issue#374_updates_from_webui
Parse update data
Merge branch 'issue#374_updates_from_webui' of github.com:schakrava/rockstor-core into schakrava-issue#374_updates_from_webui
Fix template
return current version when there are no updates available.
Add modal dialog when update is in progress
Style modal dialog for update
get current version from a different string.
Modify version string in navbar and formatting on update page
Merge branch 'issue#374_updates_from_webui' of github.com:schakrava/rockstor-core into schakrava-issue#374_updates_from_webui
Add exception handling to update and udpate-check
Merge branch 'issue#374_updates_from_webui' of github.com:schakrava/rockstor-core into issue#374_updates_from_webui