Doc: use `--type=bool` instead of `--bool`

After fb0dc3bac1 (builtin/config.c: support `--type=<type>` as preferred
alias for `--<type>`, 2018-04-18) we have a more modern way of spelling
`--bool`.

Update all instances except those that explicitly document the
"historical options" in git-config.txt. The other old-style
type-specifiers already seem to be gone except for in that list of
historical options.

Tweak the grammar a little in config.txt while we are there.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -225,7 +225,7 @@ boolean::
 	false;; Boolean false literals are `no`, `off`, `false`,
 		`0` and the empty string.
 +
-When converting value to the canonical form using `--bool` type
+When converting a value to its canonical form using the `--type=bool` type
 specifier, 'git config' will ensure that the output is "true" or
 "false" (spelled in lowercase).
 

Documentation/git-config.txt

@@ -442,9 +442,9 @@ For URLs in `https://weak.example.com`, `http.sslVerify` is set to
 false, while it is set to `true` for all others:
 
 ------------
-% git config --bool --get-urlmatch http.sslverify https://good.example.com
+% git config --type=bool --get-urlmatch http.sslverify https://good.example.com
 true
-% git config --bool --get-urlmatch http.sslverify https://weak.example.com
+% git config --type=bool --get-urlmatch http.sslverify https://weak.example.com
 false
 % git config --get-urlmatch http https://weak.example.com
 http.cookieFile /tmp/cookie.txt

Documentation/git.txt

@@ -76,7 +76,7 @@ Note that omitting the `=` in `git -c foo.bar ...` is allowed and sets
 `foo.bar` to the boolean true value (just like `[foo]bar` would in a
 config file). Including the equals but with an empty value (like `git -c
 foo.bar= ...`) sets `foo.bar` to the empty string which `git config
---bool` will convert to `false`.
+--type=bool` will convert to `false`.
 
 --exec-path[=<path>]::
 	Path to wherever your core Git programs are installed.