new functionalities for transient reduced basis

For floating point types:
"if (!fp)" is always equivalent to "if (fp == 0.0)"
"vecfp.resize(n)" is always equivalent to "vecfp.resize(n,0.0)"

In each case the former is terser and is immediately comprehensible to someone who knows all the little tricks of the language, but the latter is more long-winded but is comprehensible even if you haven't memorized every detail of boolean conversion rules or standard library APIs.