General project update & interim status of develop branch.

- Fixes in CHANGELOG.md
- Added note in README.md
- Updated package requirements.

Resolved conflicts with develop branch.

- Corrected CHANGELOG.md
- Added comment in .travis.sh
- Update for .travis.yml: gcc/g++ v5->v6

Fixed stlink support with no mass storage (#861).

Add aliased SRAM2 region in the L496 memory map (#824)

[doc/trivial] Fix st-flash manpage read example (#858)

-> CKS devices with Core ID 0x2ba01477
(Closes #756 #757 #761 #766 #769 #805)

- Updated README & CHANGELOG.
- Updated issue templates.
- Fixes in travis.yml

added several comments on the stlink software structure

Fix dead link in README.md

Since STLink 2.33.25, it is possible to flash the STLink in two modes:
- STM32 Debug + VCP
- STM32 Debug + Mass storage + VCP

When flashed in the first mode, the device id changes, but the behaviour
remains the same.
This commit thus introduces support for this new device id.

Size must be specified as hexdecimal number (as per both documentation
and implementation)

Add stlink-tools link for Debian and Ubuntu

Allow reading/writing option bytes to STM32F446 devices

Fixing verification fail for chip ID L4RX

bug fix: Flash read operation was not executed