Moved Convex theory to library.

Generalize swap_inj_on; add simps for Times; add Ex_list_of_length, log_inj; Added missing locale edges for linordered semiring with 1.

proof terms for strip_shyps, based on the version by krauss/schropp with some notable differences: * present type variables are only compared wrt. first component (the atomic type), not the duplicated sort; * extra sorts are grounded towards fixed 'a, potentially with different sorts (the original version with Name.names could cause name clashes with other present variables, too, but this should not be a problem); * deriv_rule_unconditional ensures that proof terms are always maintained independently of the "proofs" flag -- this improves robustness and preserves basic PThm proofs required for extraction attributes, e.g. in theory HOL/Extraction;