lib/sh/util.sh: echo_func: added usage

lib/sh/util.sh: $log_level_indent: changed to a single space rather than two, to avoid very deep indents as the call tree becomes more deeply nested. due to the + at the beginning of every line, a single space is enough to visualize the structure of the call tree (unlike source code, which requires more whitespace because it doesn't have a call tree structure).

lib/sh/util.sh: echo_*func aliases: increase the indent for the duration of the function call. this causes function calls to be displayed in an indented call-tree structure, which makes the verbose output much easier to understand.

bugfix: lib/sh/util.sh: recursive aliases (i.e. aliases that call a command of the same name): use "" around the command name so it isn't reexpanded if the function using the alias is copied using copy_func(). (aliases will be reexpanded every time a function is redeclared since they appear unquoted in the function definition.) this is a bug in `declare -f` for which there is no fix, necessitating the "" alias workaround instead.

lib/sh/util.sh: moved log-indent-related vars/aliases before they are first used (by log())

lib/sh/util.sh: renamed inc_log_level/dec_log_level to shorter log++/log--

lib/sh/util.sh: renamed inc_log_level/dec_log_level to shorter log++/log--

lib/sh/util.sh: renamed cmd_indent to just indent now that indent is not being used for the PS4 level

*{.sh,run}: multi-command aliases: enclose in {} so the alias can be used after ||

lib/sh/util.sh: renamed indent->PS4++ , outdent->PS4-- because these relate just to the PS4 length, not to the (whitespace-based) log_indent