#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 merge 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.

Closes #85 (closed)