Added 121 formulas: NA, CHOOSE, GCD, TRIM, LCM, GAMMALN, PERCENTILE, QUARTILE, PRODUCT, QUOTIENT, UPLUS, UMINUS, STDEV, STDEVA, STDEVP, STDEVPA, ISTEXT, ISLOGICAL, ISNUMBER, ISNONTEXT, MROUND, FACTDOUBLE, FREQUENCY, GROWTH, TRIMMEAN, SLOPE, LOWER, UPPER, STANDARDIZE, SMALL, LARGE, KURT, INTERCEPT, FORECAST, SYD, SLN, NPV, NPER, NOMINAL, MIRR, IRR, IPMT, FV, ISEMAIL, ISURL, POISSON, LINEST, PERCENTRANK, PERCENTRANK.INC, PERCENTRANK.EXC, NORMSINV, NORMSDIST, NORMDIST, NORMINV, NEGBINOMDIST, GEOMEAN, HARMEAN, CONFIDENCE, N, UNARY_PERCENT, MULTINOMIAL, BINOMDIST, COVAR, ISREF, ERRORTYPE, ERROR.TYPE, ISBLANK, ISERR, ISERROR, ISNA, TYPE, COLUMN, ROW, T, PPMT, WEIBULL, VARPA, VARP, VARA, VAR, PERMUT, RSQ, SKEW, STEYX, PROB, MODE, RANK, RANK.AVG, RANK.EQ, LOGNORMDIST, TDIST, TO_DATE, TO_PERCENT, TO_DOLLAR, TO_TEXT, ISFORMULA, IFERROR, ADDRESS, COLUMNS, ROWS, ROMAN, TEXT, FVSCHEDULE, PV, RATE, SUBTOTAL, HYPGEOMDIST, ZTEST, FIND, JOIN, LEN, LEFT, RIGHT, SEARCH, REPT, VALUE, CLEAN, MID, PROPER, REPLACE, and SUBSTITUTE.

Most functions handle Cells gracefully, converting to primitives where necessary, and returning Cells where necessary.

Numbers can now be entered in scientific-notation format.

Pulled OpenOffice license into separate file for clarity.

Documentation and cleanup of Parser.ts