Merge pull request #1280 from leifg/fix-parsing-of-0

fix: make sure value("0") works

Merge pull request #1242 from leifg/catch-date-parsing-errors

fix: guard against date parsing errors

Merge pull request #1239 from leifg/make-time-comparable

Make time comparable

Merge pull request #1169 from paustint/bug/1168

Ensure exponent operator is an integer

Merge pull request #1098 from leifg/bugfix-for-if-condition

Make unary operator possible in concatenated logic expressions

Merge pull request #1040 from leifg/fix-parser

Merge pull request #971 from leifg/implement-is-null

feat: implement isnull and nullvalue

Merge pull request #970 from leifg/fix-concatenation-with-null

fix: implement concatenation for string and null value

Merge pull request #939 from leifg/allow-brackets-in-variable-names

Properly type check in multiply/divide/exponentiate

Merge pull request #938 from leifg/allow-brackets-in-variable-names

fix: allow brackets for identifier names