Rewrite entire plugin management system

- This encapsulates all plugin related functionalities into the plugins/
  folder (and pluginconfig/) instead of relying on utility file.
- It also renames utility/plugins.lua to a more sensible
  plugins/packer.lua as it actually only applies for packer plugin
  manager.
- The plugins.lua file is now split into 2 files, first holding the list
  of all plugins plugins/plugin_list.lua and second one holding the
  logic of bootstrapping and running startup on packer.

home/.config/nvim/lua/plugins/plugin_list.lua

@@ -0,0 +1,62 @@
+local vim = require("vim")
+local fn = vim.fn
+
+local plugin_directory = fn.stdpath("config") .. "/lua/pluginconf"
+
+-- Return the line (string) to be executed with lua that loads in given plugin file.
+-- This is useful for the `config` or `setup` parameters of packer's use to source
+-- both `.vim` and `.lua` files.
+-- Expects a `plugin_file` which is a relative path from the `plugin_directory` folder.
+local function get_plugin_file(plugin_file)
+    local source_line = string.format('source %s/%s', plugin_directory, plugin_file)
+    return string.format("vim.fn.execute('%s')", source_line)
+end
+
+
+-- Define packer plugins
+-- The individual tables will get passed into the packer's use function
+local plugin_list = {
+    { "airblade/vim-gitgutter" },
+    { "dhruvasagar/vim-table-mode" },
+    { "tmhedberg/SimpylFold" },
+    { "wakatime/vim-wakatime" },
+    { "mhinz/vim-startify" },
+    { "ryanoasis/vim-devicons" },
+    { "sheerun/vim-polyglot", setup = get_plugin_file("polyglot.lua") },
+    { "vimwiki/vimwiki", config = get_plugin_file("vimwiki.lua") },
+    { "tpope/vim-commentary", config = get_plugin_file("commentary.lua") },
+    { "junegunn/fzf", run = function() fn['fzf#install']() end },
+    { "tomasiser/vim-code-dark", config = get_plugin_file("vim-code-dark.lua") },
+    {
+        "vim-airline/vim-airline",
+        config = get_plugin_file("airline.lua"),
+        requires = { "vim-airline/vim-airline-themes", opt = true },
+    },
+    {
+        "preservim/nerdtree",
+        config = get_plugin_file("nerdtree.lua"),
+        requires = {
+            { "Xuyuanp/nerdtree-git-plugin", opt = true },
+            { "tiagofumo/vim-nerdtree-syntax-highlight", opt = true },
+        },
+    },
+    {
+        "mfussenegger/nvim-dap",
+        config = get_plugin_file("nvim-dap.lua"),
+        requires = { "mfussenegger/nvim-dap-python", opt = true },
+    },
+    {
+        "junegunn/fzf.vim",
+        config = get_plugin_file("fzf.lua"),
+        after = "fzf",
+        requires = { "stsewd/fzf-checkout.vim", opt = true },
+    },
+    {
+        "neoclide/coc.nvim",
+        branch = "release",
+        config = get_plugin_file("coc.vim"),
+        requires = { "antoinemadec/coc-fzf", opt = true },
+    },
+}
+
+return plugin_list