New CLI Flag --devel To Include Development/Prerelease Versions of Charts (#139)

* Include devel Flag for Toggling Dev Chart Versions

The flag `--devel` for enabling/disabling dev versions
of charts in following endpoints:
1. /api/helm/repositories/kafka-operator
2. /api/helm/repositories/versions
3. /api/helm/repositories/latestver

Signed-off-by: Bhargav Ravuri <bhargav.ravuri@infracloud.io>

* Run Tests on Devel Flag Related Changes

Signed-off-by: Bhargav Ravuri <bhargav.ravuri@infracloud.io>

---------

Signed-off-by: Bhargav Ravuri <bhargav.ravuri@infracloud.io>

pkg/dashboard/objects/testdata/repositories-malformed-manifest.yaml

@@ -0,0 +1,12 @@
+apiVersion: ""
+generated: "0001-01-01T00:00:00Z"
+- repositories:
+- caFile: ""
+  certFile: ""
+  insecure_skip_tls_verify: false
+  keyFile: ""
+  name: charts
+  pass_credentials_all: false
+  password: ""
+  url: https://charts.helm.sh/stable
+  username: ""