wiki: Fix in->mm and mm->in conversions

Fixes funny accidents like `1602 mm` instead of `160.02 mm`.

Change-Id: I595eec0ad40fa94693bdef03f55422788f74a451

Author: luk1337

Diff for: _includes/snippets/dimensions.html

@@ -1,6 +1,6 @@
 {%- if modelname %}
 <b>{{ modelname }}</b><br/>
 {%- endif %}
-{{ dimension_data.height }} mm ({{ dimension_data.height | divided_by: 25.4 | round: 2 | remove: ".0" }} in) (h)<br/>
-{{ dimension_data.width }} mm ({{ dimension_data.width | divided_by: 25.4 | round: 2 | remove: ".0" }} in) (w)<br/>
-{{ dimension_data.depth }} mm ({{ dimension_data.depth | divided_by: 25.4 | round: 2 | remove: ".0" }} in) (d)
+{{ dimension_data.height }} mm ({{ dimension_data.height | mm_to_in }} in) (h)<br/>
+{{ dimension_data.width }} mm ({{ dimension_data.width | mm_to_in }} in) (w)<br/>
+{{ dimension_data.depth }} mm ({{ dimension_data.depth | mm_to_in }} in) (d)

Diff for: _includes/snippets/screen.html

@@ -1,6 +1,6 @@
 {%- if modelname %}
 <b>{{ modelname }}</b><br/>
 {%- endif %}
-{{ screen_data.size }} in ({{ screen_data.size | times: 25.4 | round: 2 | remove: ".0" }} mm)<br/>
+{{ screen_data.size }} in ({{ screen_data.size | in_to_mm }} mm)<br/>
 {{ screen_data.resolution }} ({{ screen_data.resolution | ppi: screen_data.size }} PPI)<br/>
 {{ screen_data.technology }} {% if screen_data.refresh_rate %}(max. {{ screen_data.refresh_rate }} Hz){% endif %}

Diff for: _plugins/jekyll-size.rb

@@ -0,0 +1,13 @@
+module Jekyll
+  module Size
+    def in_to_mm(value)
+      (value * 25.4).round(2).to_s().chomp('.0')
+    end
+
+    def mm_to_in(value)
+      (value / 25.4).round(2).to_s().chomp('.0')
+    end
+  end
+end
+
+Liquid::Template.register_filter(Jekyll::Size)