initremote: Support --json and --json-error-messages

Including special --whatelse handling.

Otherwise, it seems unlikely to be too useful, but who knows.

Refactored code to call starting before displaying error messages.
This makes the error messages be captured by --json-error-messages

Sponsored-By: the NIH-funded NICEMAN (ReproNim TR&D3) project

doc/todo/--json_for_unannex__and_ideally_any_other_command_.mdwn

@@ -39,12 +39,12 @@ These commands have been updated to support --json:
 * git-annex-importfeed
 * git-annex-merge
 * git-annex-upgrade
+* git-annex-initremote
 
 Provisional list of commands that don't support --json and maybe should:
 
 * git-annex-configremote
 * git-annex-enableremote
-* git-annex-initremote
 
 These commands could support json, but I punted:
 

doc/todo/provide_machine_readable___40__--json__63____41___version_of_initremote_--whatelse.mdwn

@@ -57,3 +57,5 @@ Looking at the [protocol](https://git-annex.branchable.com/design/external_speci
 
 [[!meta author=yoh]]
 [[!tag projects/datalad]]
+
+> [[done]] --[[Joey]]

doc/todo/provide_machine_readable___40__--json__63____41___version_of_initremote_--whatelse/comment_2_e9647b34aa79c414faf0f57ba17e6af4._comment

@@ -0,0 +1,14 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 2"""
+ date="2023-05-10T16:56:37Z"
+ content="""
+I'm still not seeing much of an application for this, but since I've been
+adding --json support to most git-annex commands anyway recently, and got
+to initremote, I did go ahead and make --whatelse --json work.
+
+Currently only the field name and description, and a description of the
+allowed values are in there. It might be possible to add more information
+like type or required or not, but I'd want to work with someone who was
+consuming that information to do that.
+"""]]