all: Add/improve config options

As part of the upstreaming effort, we need to add some extra tunings
in the package. Especially related to GRUB autosetting and Pstore
memory settings:

(a) Currently the ramoops record size and memory amount are hardcoded
in the kdump-load script - we change it here, by having these settings
on the kdump config file;

(b) GRUB autosetting is pretty simple and everything is hardcoded.
We hereby add a bunch of configurable settings in the kdump conf file,
in order we can customize the GRUB handling, to make it work in both
Arch and SteamOS.

While at it, fixed some related comments and renamed some variables,
usually dropping KDUMP_ name when it applies to pstore as well.
Also, bumped the crashkernel memory from 192M to 256M - recent kernels
demand more memory, let's play safe.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>

kdump-collect.sh

@@ -23,7 +23,7 @@ done
 
 VMCORE="/proc/vmcore"
 KDUMP_TIMESTAMP=$(date -u +"%Y%m%d%H%M")
-KDUMP_FOLDER="/kdump_path/${KDUMP_FOLDER}/crash/${KDUMP_TIMESTAMP}"
+KDUMP_FOLDER="/kdump_path/${MOUNT_FOLDER}/crash/${KDUMP_TIMESTAMP}"
 
 #  Bail out in case we don't have a vmcore, i.e. either we're not kdumping
 #  or something is pretty wrong and we wouldn't be able to progress.