Small improvements to docs

Lost allocs replaced even if deployment failed

This PR fixes an incorrect placement of the update stanza in the task
and also links from the env stanza into an example of using the template
block to generate dynamic environment variables.

Document <task> network env vars

Looks like I accidently dropped them when combining env var listings in
PR #2709

Update revert.html.md.erb

wrong command

Spelling and grammar fixes for manual bootstrap guide.

This PR allows the scheduler to replace lost allocations even if the job
has a failed or paused deployment. The prior behavior was confusing to
users.

Fixes https://github.com/hashicorp/nomad/issues/2958

#2563 fixed pending state for allocations with terminal status

This reverts commit 9f2ea928.

Remove people from community section

This is going to be replaced with dynamic content from our CMS in the
future, but we agreed to remove it in the interim.

add third party client library link for python

meta: Ignore IntelliJ IDEA/Gogland project files

meta: Set main.VersionPrerelease="dev"

"it's" -> "its"

Rename GNUMakefile to Makefile

For most projects using this versioning system, making a commit bumping
the version and re-adding the development tag is part of the release
SOP (certainly it was for Terraform!). I'm not sure why it didn't happen
here, but without this, all development builds show up as Nomad v0.6.0
with no dirty marker or commit marker.

add job creating json sample in jobs api doc

Document update stanza for system scheduler.

Added a sentence about job anti-affinity; Reflowed

Distinct Property supports arbitrary limit

Document Purge parameter on deregister request

This will create a concrete mention of job anti-affminity in the Nomad documentation. The only place we discuss it currently is in a similar sentence on the website itself.  I borrowed liberally from that sentence in crafting this line.

More why for the -orphan flag