View expression: export features

[denisrosset]

Add three buttons to each of (FP table, CG table, C table, FP expr, CG expr, C expr):

• MAT: export as MAT file, including a matrix of coefficients and cell array of strings representing the ordering of terms
• RAW: raw ASCII representation (ex: numbers separated by commas, or plain text representation of expression)
• TeX: export as TeX source code