ref: #756, set cell as blank when SetCellValue with nil #756, new formula fn: BITAND, BITLSHIFT, BITOR, BITRSHIFT, BITXOR

This closes #785, support to change tab color; new formula function: FISHER, FISHERINV, GAMMA, GAMMALN, MIN, MINA, PERMUT

lint issue fixed and new formula function: ATAN, AVERAGE, AVERAGEA, CONCAT, CONCATENATE, COUNT, COUNTBLANK, MAX

This closes #752, fix incorrectly merged cells on duplicate row, and new formula function: LOWER, PROPER, UPPER

Fix #701, init new formula function AND and OR, prevent formula lexer panic on retrieving the top token type

- Update unit test

- styles: allow empty and default cell formats, #628

- resolve ineffectual assignment
- handle exception with invalid formula
- update range resolver

#65 fn: CSCH, DECIMAL, DEGREES, EVEN, EXP, FACT, FACTDOUBLE, FLOOR, FLOOR.MATH, FLOOR.PRECISE, INT, ISO.CEILING, LN, LOG, LOG10, MDETERM