Modify some paragraph text and chart data

1. Add 'Free' and 'Used' data according to:
    Free = MemFree + Cached + SwapCached - Mlocked - Shmem
    Used = AnonPages + Slab + VmallocAlloc + Mlocked + Shmem + KernelStack + PageTables + KGSL_ALLOC + ION_ALLOC
2. Change some text and style

Signed-off-by: Chun Chen <chun.chen@archermind.com>