Add v2.0.0 release notes (ESMValGroup#1781)

Merge pull request ESMValGroup#1628 from ESMValGroup/version

Increase version to v2.0.0b4

Merge pull request ESMValGroup#1568 from ESMValGroup/version

Increase version to v2.0.0b3

Merge pull request ESMValGroup#1502 from ESMValGroup/increase_version

Increase version to v2.0.0b2

Merge pull request ESMValGroup#1302 from ESMValGroup/conda_build2

Various updates to dependencies and CircleCI configuration

Merge pull request ESMValGroup#1162 from ESMValGroup/version2_develop…

…ment

Release v2.0.0b0

Merge pull request ESMValGroup#1104 from ESMValGroup/version2_develop…

…ment

v2.0a2 release

Merge pull request ESMValGroup#558 from ESMValGroup/version2_development

Version 2.0a1 release

Merge pull request ESMValGroup#427 from ESMValGroup/version2_development

Version 2: Merge development branch

Convert MASTER file to unix format (no windows-like line terminators)