fix(version): Handle pkgbase with '.' correctly

For pkgbases with '.' in the name, the TOML-section must be wrapped in
double quotes in order for it not to be parsed as a supersection and a
subsection. This case was not properly handled by checks for if the
TOML-file contains a pkgbase section, and for if the TOML-file contains
superfluous sections. Address this by handling optional double quotes in
the greps related to said checks.

This was discovered in the AUR package ruby-cool.io and the issue can be
reproduced with the following minimal PKGBUILD and .nvchecker.toml file:

    $ cat PKGBUILD
    pkgname=ruby-cool.io
    pkgver=1.8.0
    $ cat .nvchecker.toml
    ["ruby-cool.io"]
    source = "gems"
    gems = "cool.io"

Before the fix:

    $ pkgctl version check
    Failure
     x ruby-cool.io: missing pkgbase section in .nvchecker.toml: ruby-cool.io

After the fix:

    $ pkgctl version check
    GEN lib/version/check.sh
    Out-of-date
     ✓ ruby-cool.io: current version 1.8.0 is latest

Component: pkgctl version check

src/lib/version/check.sh

@@ -260,13 +260,13 @@ nvchecker_check_config() {
 	done
 
 	# check if the config contains a pkgbase section
-	if [[ -n ${pkgbase} ]] && ! grep --max-count=1 --quiet "^\\[${pkgbase}\\]" < "${config}"; then
+	if [[ -n ${pkgbase} ]] && ! grep --max-count=1 --extended-regexp --quiet "^\\[\"?${pkgbase}\"?\\]" < "${config}"; then
 		printf "missing pkgbase section in %s: %s" "${config}" "${pkgbase}"
 		return 1
 	fi
 
 	# check if the config contains any section other than pkgbase
-	if [[ -n ${pkgbase} ]] && property=$(grep --max-count=1 --perl-regexp "^\\[(?!${pkgbase}\\]).+\\]" < "${config}"); then
+	if [[ -n ${pkgbase} ]] && property=$(grep --max-count=1 --perl-regexp "^\\[(?!\"?${pkgbase}\"?\\]).+\\]" < "${config}"); then
 		printf "none pkgbase section not supported in %s: %s" "${config}" "${property}"
 		return 1
 	fi