Trainers Rebalanced and Unlocked

An attempt to make trainers more balanced, diverse and fun. Introduces 4 changes.

1. Less is More: a restriction which makes finding new trainers more rewarding

Single NPC can train you not more than once per each skill. To continue training you need to find another trainer, which makes

trainers useful and exploration more rewarding. Your progress is more gradual and spaced out over time, as it depends on how many trainers you're able to find, rather than how much gold you accumulate. This restriction is in place to make the game more challenging overall but, most importantly, to prevent trainers from becoming boring and game-breaking, as otherwise it's possible to abuse one master trainer from the beginning and effortlessly convert all your gold directly into levels, potentially becoming overpowered in just one training session. You don't have to self-restrain anymore - this mod does it for you. But! There are some fun facilitations to compensate for this nerf.

2. Trainers can teach more than 1 level per click

Trainers will raise 1-5 skill levels, depending how skilled they are (master trainers will teach 5 levels, whereas trainers from 1-30 skill value range will teach 1 level), making trainers' skill diversification more visible. Of course, training price is adjusted accordingly: master trainers are most expensive but they grant you more levels, so the end result is similar as training with few mediocre trainers, there is no need to min-max. The trainer tier formula is: ÷ 20, rounding the halves down. The result determines how many skill levels the trainer will teach you. In example:

NPC trainer with Destruction skill level 90 will raise your Destruction skill by 4 levels (90 ÷ 20 = 4. 5). And it would cost the same as 4 regular separate training sessions for your current level, so a single training at a high-tier trainer is slightly more cost-effective than 4 separate training sessions. In the unmodded game, most trainers are at tier level 3, though. There are no tier-1 trainers, unless you unlock their lower skills (described in change #4).

3. Surplus XP is not wasted when leveling up

Normally, when you train a skill in which you've already made some progress, the progress bar resets at the start of a new level (to 0/100), meaning your surplus progress was effectively wasted. Here, the progress is remembered and carried over to the next level, no matter if the skill was increased by 1, or by 5 levels. For simplicity, it assumes the skill progress is linear, but in fact higher levels should have bigger requirements, which should actually slightly decrease the carried over progress, but in the face of trainer restrictions, let's gi