Gulpfile: download help assets

Implement a new build step 'build-help-assets' that downloads
help pages from Confluence and stores them in `client/www/help/*.json`.

The list of pages to download is configured in `client/help.json`.

The content of help pages is processed using `cheerio` and
all relative Confluence links are resolved to absolute ones.
client: use the local help files

Rework `slPopoverHelp` to use the local copy of Confluence docs.

Re-enable help for "Build universal" and "Build git".
Merge pull request #534 from strongloop/feature/build-help-assets

#511 - Build help assets
fix error object reference in try/catch block
Merge pull request #550 from strongloop/fix/build-error-gulp-help-files

fix error object reference in try/catch block
update pid module to reflect rest api changes
Merge pull request #549 from strongloop/fix/update-pid-filter-component

Fix/update pid filter component
add better error handling for build and deploy

- add message type to form messages
- show an error if you can't build properly
- handle error during deploy process
- add todo for checking status of deploy
bin/cli: rename Studio to Arc

Replace all references of Studio with Arc.

Remove the requirement to run Arc in a LoopBack application,
Arc supports non-loopback apps too.
Remove "npm install loopback-explorer" log

loopback-explorer is a devDependency that is not included when
`strong-arc` is installed globally, for example via

    npm install -g strongloop

This commit changes the explorer boot script to print the message
only when the server was started via `app.listen`.
Remove auto-generated strongloop.css from git

A fixup for fefbb1ea that added a build task to generate strongloop.css
from LESS, but did not remove the generated file from version control.
Merge pull request #553 from strongloop/fix/git-files

Remove auto-generated strongloop.css from git
add better error handling for build and deploy

- add message type to form messages
- show an error if you can't build properly
- handle error during deploy process
- add todo for checking status of deploy
Merge branch 'feature/build-deploy-ui' of github.com:strongloop/strong-studio into feature/build-deploy-ui
Merge pull request #548 from strongloop/feature/build-deploy-ui

add better error handling for build and deploy

#72
Merge pull request #552 from strongloop/fix/help-messages

Fix help messages
refactor profiler references to new endpoints

- change processId to pid
- change api endpoints
swap file and remote in profiler
remove deprecated code
Merge pull request #556 from strongloop/feature/profiler-navbar

refactor profiler references to new endpoints

#strongloop/scrum-loopback/73