: local setting of log_level: use log_local instead of relying on the log aliases, so that these aliases can instead be used for wrapping commands (the more common use case)

bugfix: lib/sh/util.sh: verbosity_compat alias: need to use `declare verbosity="$verbosity"` instead of `declare verbosity`, which would just clear $verbosity

bugfix: lib/sh/util.sh: verbosity_min alias: need to use `declare verbosity="$verbosity"` instead of log_local now that verbosity is not one of the vars changed by log++

lib/sh/util.sh: log+(): use easier-to-understand log_local instead of prefix-assignments to limit assignments to the invoked command

lib/sh/util.sh: log+(): use easier-to-understand log_local instead of prefix-assignments to limit assignments to the invoked command

: use clog instead of "log*"

bugfix: lib/sh/util.sh: log+(): removed spurious ; between setting of PS4 and log_level, which was causing erratic mismatches between PS4 and log_level. (the ; caused $PS4 to be set in the caller when invoked via one of the clog* aliases, rather than being passed as a command-specific env var.)

lib/sh/util.sh: $verbosity: stay constant at what the user set it to instead of changing in tandem with $log_level, to facilitate debugging verbosity/log_level-related issues

lib/sh/util.sh: log+(): usage: use aliases instead of ""-ed function names

added schemas/VegCore.ERD.pdf symlink for easy access