Feature/unformated logging benchmark

[rfernandes]

Not calling, flag / setting reset on every log line yields significant performance benefits. This does mean that changes to io fields (width, spacing, good, etc) will persist across log calls, and that it's now the responsibility of the caller to restore whatever modifiers are set. OStringStream reuse is now somewhat similar to the stringstream reuse idiom:

stringstream ss;
(...)
ss.str("");
ss.clear();

with

OStaticStream<7> os;
(...)
os.reset()
os.clear()

Benchmark results (Before/After):

NAME	COUNT	MIN	%50	%95	%99	%99.9	%99.99
log_formated	95225000	0.03	0.03	0.032	0.032	0.036	0.041
log_unformated	96840000	0.028	0.03	0.031	0.032	0.042	0.043

NAME	COUNT	MIN	%50	%95	%99	%99.9	%99.99
log_formated	167730000	0.017	0.017	0.018	0.018	0.02	0.02
log_unformated	170380000	0.017	0.017	0.017	0.018	0.019	0.02