Flesh out manual-install.md intro and small fix-ups.
Flesh out manual-install.md intro and small fix-ups.

- Added an introduction
- Put in System Requirements under Prerequisites
- Changed order of tar arguments to 'official' order even though Linux DTRT both ways
- Add sudo where necessary
- Changed commands to refer to $CWD instead of $HOME
davidwadden/lattice,datachand/lattice,svrc-pivotal/lattice,Klaudit/lattice,svrc-pivotal/lattice,Klaudit/lattice,svrc-pivotal/lattice,SrinivasChilveri/lattice,datachand/lattice,Klaudit/lattice,davidwadden/lattice-release,davidwadden/lattice,cloudfoundry-incubator/ltc,felipeg48/lattice,datachand/lattice,felipeg48/lattice,SrinivasChilveri/lattice,SrinivasChilveri/lattice,datachand/lattice,cloudfoundry-incubator/ltc,davidwadden/lattice-release,Klaudit/lattice,svrc-pivotal/lattice,SrinivasChilveri/lattice