Exit immediately if --parent-pid doesn't look like an integer.

If you pass "--parent-pid foobar", then we immediately log an error
message and exit. This check happens via `parseInt` rather than testing
for exceptions in `process.kill(parentPid, 0)` because `process.kill`
converts its pid argument to an integer, so `process.kill('foobar', 0)`
returns true just as `process.kill(0, 0)` does.
Fix check for valid parent id.

Parse as decimal (which means you can't specify --parent-pid in hex,
that's fine). And convert back to string to check that the whole string
was parsed as an int (i.e. "123foobar" should not be converted to
"123").

Thanks Slava and Avital.
Factor out check for valid --parent-pid and add tests.
Simplify `validPid`, thanks Ben
we don't have an apprecord for old releases, so if a project is using an old version, we have to be careful
Resolve leftover merge conflicts in History.md
Use `Template.headline.helpers` syntax in docs.

This change was made when we deprecated `Template.headline.foo` syntax
but was lost in the merge.
Fix docs 'depthIs' helper
docs: clarify `Meteor.wrapAsync` client usage
Fix login service configuration wizards.

These were broken by the Template.foo.bar -> Template.foo.helpers({ bar:
... }) transformation. `fields` is a property on the template object,
not a helper.
Remove duplicated code in 'reload'.

This code was factored out a long time ago, but got duplicated by
accident in a merge conflict resolution (611298f).

Also lay some groundwork for a unit test.
Add 'reload' unit test
enterJob for installing cordova plugins
Cache (successful) ensure_android_bundle calls
Implement a `meteor debug` command.

Summary:
The `node-inspector` NPM package was added to the dev_bundle by this
recent commit: 64a624ae5c36a30c10e20216400f7e751d4963b2

Task: https://app.asana.com/0/15750483766338/16241466809965

Test Plan:
Add `debugger` statements to server code, run `meteor debug`, visit the
node-inspector URL in a browser, continue the application, and verify that
the debugger stops at the `debugger` statements that were set.

Reviewers: nim, slava, emily, avital

Differential Revision: https://phabricator.meteor.com/D827