Standardize logging method to 'exec & tee'.
The SDP has two flavors of logging, a legacy method that requires
redirects of stdout and stderr on any and all commands executed by
scripts (and is a source of bugs), and the superior 'exec & tee'
mechanism used in build systems. The 'exec & tee' mechanism:
* Reliably ensures no important output is lost.
* Greatly reduces code readability by removing redirects.
* Reduces maintenance effort, as developers no longer need to
remember redirects for all commands.
* Standardizes look & feel for users, with consistent logging
options (with only planned differences, e.g. scripts that run
from crontab and only generate logs vs. scripts intended to
run directly from the command line).
* Removes a source of SDP logging bugs.