#85 Improved development process documentation.

 - We don't use epics. We use linked issues instead.
 - Clarified that removing things is also an enhancement.
 - Updated planning information to reflect our real-life process.
 - Explained issue/branch ownership rules/process.
 - Explained that we ideally address only one issue per branch.
 - Added our view on branch vs rebase.
 - Added that commit/push often is required as per EF rules.
 - Added info on using multiple commits, especially for renames/moves.
 - Various other small textual improvements.