Revamp the documentation of the submit strategies
Revamp the documentation of the submit strategies

* Merge the 'Submit Type' section into the section that describes the
  'submit.action' configuration parameter.
* Make it clear that 'submit action', 'submit type' and also
  'submit strategy' are all synonymous terms.
* Add a hint explaining that the values to be set for submit.action in
  project.config indeed contain spaces (e.g. it's 'merge if necessary'
  and not 'merge_if_necessary').
* Keep existing anchors so that they continue working.
* Fix name of the 'Merge Always' submit action, which was wrongly
  documented as 'Always Merge'.
* Explicitly mention that 'cherry pick' is the only action that ignores
  dependencies.
* Order the submit actions by importance, starting with the most used
  submit action 'merge if necessary' and ending with the least
  recommended submit actions 'fast-forward-only' and 'cherry-pick'.
* Fix various formatting issues.
* Consistently wrap lines after 80 characters.

This revamp is just a first step to rework this documentation and
further improvements by follow-up changes are necessary. E.g. the
descriptions of the different submit actions have not been updated yet
and are still suboptimal and inconsistent.

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Release-Notes: skip
Change-Id: I0dd66d71f3989308cba32330412e4f90052f7a86

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