support fragment caching

[darnocian]

<% cache 'mykey' %>
      content to be cached
<% end %>

so if we have something like:

<% cache 'products'; for product in products %>
     <% product.id %> <% product.name %>
<% end ; end %>

this would allow the list of products to be cached.

helper methods:

• invalidateCache(id)
• getCacheTimeS(id)

context methods:

• invalidateCache(id)

Need to provide:

• cache provider (memory, redis, memcache, db)

var redisCfg := RedisConfig.Create();
with redisCfg  do
begin
    host := '192.168.1.42';
    port := 4242;
end;
context.cacheProvider := RedisCache(redisCfg);